1. Field of the Invention
The present invention relates generally to telecommunications systems and methods for managing traffic channels in a wireless network, and specifically to prioritizing subscribers' use of the traffic channels.
2. Background and Objects of the Present Invention
Cellular telecommunications is one of the fastest growing and most demanding telecommunications applications ever. Today it represents a large and continuously increasing percentage of all new telephone subscriptions around the world. A standardization group, Global System for Mobile Communication (GSM), was established in 1982 to formulate the specifications for mobile cellular radio systems.
With reference now to FIG. 1 of the drawings, there is illustrated a Public Land Mobile Network (PLMN), such as cellular network 10, which in turn is composed of a plurality of areas 12, each with a Mobile Services Center (MSC) 14 and an integrated Visitor Location Register (VLR) 16 therein. The MSC/VLR areas 12, in turn, include a plurality of Location Areas (LA) 18, which are defined as that part of a given MSC/VLR area 12 in which a Mobile Station (MS) 20 may move freely without having to send update location information to the MSC/VLR area 12 that controls the LA 18. Each Location Area 12 is divided into a number of cells 22. Mobile Station (MS) 20 is the physical equipment, e.g., a car phone or other portable phone, used by mobile subscribers to communicate with the cellular network 10, each other, and users outside the subscribed network, both wireline and wireless. The MS may also include a Subscriber Identity Module (SIM) 13, which provides storage of subscriber related information, such as a subscriber authentication key, temporary network data, and service related data (e.g. language preference).
The MSC 14 is in communication with at least one Base Station Controller (BSC) 23, which, in turn, is in contact with at least one Base Transceiver Station (BTS) 24. The BTS is the physical equipment, illustrated for simplicity as a radio tower, that provides radio coverage to the geographical part of the cell 22 for which it is responsible. It should be understood that the BSC 23 may be connected to several base transceiver stations 24, and may be implemented as a stand-alone node or integrated with the MSC 14. In either event, the BSC 23 and BTS 24 components, as a whole, are generally referred to as a Base Station System (BSS) 25.
With further reference to FIG. 1, the PLMN Service Area or cellular network 10 includes a Home Location Register (HLR) 26, which is a database maintaining all subscriber information, e.g., user profiles, current location information, International Mobile Subscriber Identity (IMSI) numbers, and other administrative information. The HLR 26 may be co-located with a given MSC 14, integrated with the MSC 14, or alternatively can service multiple MSCs 14, the latter of which is illustrated in FIG. 1.
The VLR 16 is a database containing information about all of the Mobile Stations 20 currently located within the MSC/VLR area 12. If a MS 20 roams into a new MSC/VLR area 12, the VLR 16 connected to that MSC 14 will request data about that Mobile Station 20 from the HLR database 26 (simultaneously informing the HLR 26 about the current location of the MS 20). Accordingly, if the user of the MS 20 then wants to make a call, the local VLR 16 will have the requisite identification information without having to reinterrogate the HLR 26. In the aforedescribed manner, the VLR and HLR databases 16 and 26, respectively, contain various subscriber information associated with a given MS 20.
The digital GSM system uses Time Division Multiple Access (TDMA) to handle radio traffic in each cell 22. Each TDMA communication frame is divided into eight separate time slots, forming eight physical channels for communications. Logical channels are then mapped onto these physical channels. Examples of logical channels include Traffic Channels (TCH) and Control Channels (CCH).
A great deal of information must be transmitted between the BTS 24 and the MS 20, e.g., user data and control signaling. Different types of information are transmitted on the physical channels in a certain order. For example, speech is sent on a Traffic Channel (TCH), which during the transmission is allocated a certain physical channel. Traffic channels can be either full rate or half rate. One full rate TCH occupies one physical channel, while two half rate TCHs can share one physical channel.
In the GSM system, TCHs are generally considered the most precious of resources. In congested areas and during peak times of use, there may be no available TCHs, thereby preventing subscribers from placing potentially important calls. An operator can increase the number of TCHs by either introducing more hardware or using more frequency channels in a cell. However, both of these techniques are expensive for the operator.
It is therefore an object of the invention to allow for efficient use of the TCHs which both meets the subscriber's expectations and immediate needs, and produces revenue for the cellular operator.